Resumen Introducción. La enfermedad de la necrosis aguda del hepatopáncreas (AHPND, por sus siglas en inglés) es producida por bacterias Vibrio parahaemolyticus que poseen un plásmido con genes que codifican las toxinas pirA y pirB. La enfermedad se caracteriza por descamación masiva de las células epiteliales del hepatopáncreas, así como la atrofia y decoloración de ese órgano. Los camarones enfermos presentan anorexia y muestran un intestino vacío, debilidad, decoloración del cuerpo y altas mortalidades. Objetivo. Determinar la prevalencia de Vibrio parahaemolyticus causante de AHPND en fincas de camarones en la zona del Pacífico de Costa Rica. Materiales y métodos. Durante los años 2019 y 2020, se recolectaron camarones (Penaeus vannamei) y agua de estanques de 32 fincas localizadas en la costa occidental del golfo de Nicoya (noroeste del país) y la costa del Pacífico Central (Puntarenas-Parrita). Los camarones recolectados en los muestreos tenían un peso de entre 7 y 15 g. El diagnóstico de la presencia de la enfermedad se analizó a nivel molecular con la reacción en cadena de la polimerasa (PCR) punto final, y diferentes protocolos e iniciadores para detectar los genes de las toxinas pirA y pirB. Además, se hizo una correlación lineal entre la presencia de AHPND y la calidad del agua con el programa estadístico R. Resultados. La presencia de Vibrio parahaemolyticus causante de AHPND ocurrió en 93,75 % (30/32) de los estanques muestreados en ambas zonas de cultivo. Conclusiones. Este trabajo confirma la presencia y amplia distribución de AHPND en agua y camarones en treinta fincas camaroneras en el Pacífico de Costa Rica.

Abstract Introduction. The acute hepatopancreas necrosis disease (AHPND) is caused by bacteria Vibrio parahaemolyticus containing a plasmid encoding the toxin genes pirA and pirB. The disease is characterized by massive sloughing of epithelial cells in the hepatopancreas, also showing atrophy and discoloration of that organ. Diseased shrimp display anorexia with empty guts, weakness, body discoloration and high mortality. Objective. To determine the prevalence of Vibrio parahaemolyticus causing AHPND in farms that grow shrimp in the Pacific zone of Costa Rica. Materials and methods. During the years 2019 and 2020, water and shrimp (Penaeus vannamei) samples were obtained from 32 farms located on the western coast of the Nicoya Gulf (Northwest Costa Rica) and the Central Pacific coast (Puntarenas-Parrita). The samples were analyzed by endpoint polymerase chain reaction (PCR) using different protocols and primers to detect the toxins pirA and pirB. Further, a linear correlation between the presence of AHPND and water quality was done using the R statistical program. Results. The presence of Vibrio parahaemolyticus causing AHPND occurred in 93.75 % (30/32) of sampled ponds in both farming areas. Conclusion. This work confirms the presence and wide distribution of AHPND in water and shrimp from thirty shrimp farms in the Costa Rican Pacific.

Resumen Introducción. Los hongos micorrícicos arbusculares (HMA) forman asociaciones simbióticas estrechas con el 90 % de las especies vegetales. Entablan un “diálogo” molecular mediante moléculas infoquímicas y de nutrientes para la regulación de esta asociación mutualista. Objetivo. Recopilar información sobre los mecanismos moleculares implicados en la comunicación entre los HMA, su planta hospedera y otros organismos edáficos. Desarrollo. La simbiosis entre los hongos micorrícicos y las plantas depende de moléculas señalizadoras específicas que permiten el reconocimiento, la señalización y la comunicación, además del contacto físico entre ambos organismos. Se describen los mecanismos de comunicación molecular y de las interacciones biológicas entre los HMA y las plantas en los diferentes tiempos de la interacción, con énfasis en la descripción de genes reguladores, proteínas y moléculas diana conocidas. También se describen interacciones moleculares con otros organismos edáficos. Conclusiones. Los mecanismos de comunicación molecular entre hongos micorrícicos y plantas son complejos y aún presentan vacíos de conocimiento que deben ser superados para comprender a cabalidad la importancia ecológica de los HMA y sus interacciones con otros organismos edáficos y así lograr su aprovechamiento.

Abstract Introduction. Arbuscular mycorrhizal fungi (AMF) form close symbiotic associations with 90 % of plant species. They engage in a molecular dialogue using infochemicals and nutrient molecules to regulate this mutualistic association. Objective. To gather information on the molecular mechanisms involved in the communication between AMF, their host plant and other soil organisms. Development. The symbiosis between mycorrhizal fungi and plants depends on specific signaling molecules that allow recognition, signaling and communication, in addition to physical contact between both organisms. The mechanisms of molecular communication and biological interactions between AMF and plants at different times of interaction are described, with emphasis on the description of currently known regulatory genes, proteins and target molecules. Additionally, molecular interactions with other soil organisms are described. Conclusions. The mechanisms of molecular communication between mycorrhizal fungi and plants are complex and still present gaps in knowledge that must be filled to fully understand the ecological importance of AMF and their interactions with other edaphic organisms, and thus achieve their use.

Abstract (Introduction): In the removal of chromium (VI) from tannery wastewater, physicochemical methods are the most used. However, these require high operating costs, and worse still, generate secondary pollutants that again require complementary treatments for their elimination. Given this, the applicability of vegetable organic biomass (VOB) emerges as an environmental alternative based on: the simplicity of its obtaining, the reduction as waste, it does not generate secondary pollutants and, above all, it removes chromium (VI). (Objective): Use VOB waste in an aerobic sequential biological reactor (SBR) for the removal of chromium (VI) in the treatment of tannery wastewater. (Methodology): 3 aerobic SBR systems were implemented; 2 controls (SBR1 and SBR2) and 1 study subject (SBR+VOB). Each system was fed with tannery wastewater (18 L) and connected to an aeration mechanism (12.7 L/min). The bacterial inoculum, a fundamental part of an SBR system, was gained from the selective culture of chromium (VI) reducing bacteria (RBCrVI) taken from the wastewater under study, and integrated into SBR2 and SBR+VOB at 0.6 g/L. The VOB was obtained from Stenotaphrum secundatum residues, fragmented, sieved, sterilized and integrated into the SBR+VOB at 1.5 g/L. (Results): The SBR+VOB system achieved the highest percentage of chromium (VI) removal (93 %), followed by SBR2 (80.1 %), and finally SBR1 (2.8 %). With respect to COD and TSS, the statistical test (Tukey) showed that there was no significant difference between the system under study and the controls, recording COD removal percentages ranging from 87.8 % to 88.4 %, and TSS ranging from 63.8 % to 69.2 %. (Conclusions): The viability of using VOB waste to remove chromium (VI) in the treatment of tannery wastewater has been evidenced. The results of this research create a promising panorama to mitigate the effects derived from inadequate management of tannery wastewater and organic solid waste.

Resumen (Introducción): En la remoción de cromo (VI) de aguas residuales de curtiembre, los métodos fisicoquímicos son los más empleados. Sin embargo, estos demandan altos costos operativos y, peor aún, generan contaminantes secundarios que nuevamente requieren tratamientos complementarios para su eliminación. Ante ello, la aplicabilidad de la biomasa orgánica vegetal (BOV) emerge como una alternativa ambiental sobre la base de: la simplicidad de su obtención, la disminución como residuo, no genera contaminantes secundarios y, sobre todo, de remover cromo (VI). (Objetivo): Usar residuos de BOV en un reactor biológico secuencial (RBS) aerobio, para la remoción de cromo (VI) en el tratamiento de agua residual de curtiembre. (Metodología): Se implementaron 3 sistemas RBS aerobios; 2 controles (RBS1 y RBS2) y 1 materia de estudio (RBS+BOV). Cada sistema fue alimentado con agua residual de curtiembre (18 L) y conectado a un mecanismo de aireación (12.7 L/ min). El inóculo bacteriano, parte fundamental de un sistema RBS, se obtuvo a partir del cultivo selectivo de bacterias reductoras de cromo (VI) (BRCrVI), tomadas del agua residual en estudio e integradas al RBS2 y RBS+BOV a 0.6 g/L. La BOV se obtuvo de residuos de Stenotaphrum secundatum, fragmentado, tamizado, esterilizado e integrado al RBS+BOV a 1.5 g/L. (Resultados): El sistema SRB+BOV alcanzó el mayor porcentaje de remoción de cromo (VI) (93 %), seguido por SBR2 (80.1 %) y, por último, de RBS1 (2.8 %). Con respecto a la DQO y SST, la prueba estadística (Tukey) arrojó que no había diferencia significativa entre el sistema en estudio y los controles, por lo que registró porcentajes de remoción de DQO que van de 87.8 % a 88.4 % y SST que van de 63.8 % a 69.2 %. (Conclusiones): Se ha evidenciado la viabilidad del aprovechamiento de residuos de BOV para remover cromo (VI) en el tratamiento de agua residual de curtiembre. Los resultados de la presente investigación crean un panorama prometedor para mitigar los efectos derivados de la inadecuada gestión de las aguas residuales de curtiembre y de los residuos sólidos orgánicos.

ABSTRACT: The success of endodontic treatments is related to the neutralization of bacteria and their toxins, inside and outside the root canal system of a tooth. Usually this is achieved, under ideal conditions, by means of a chemical-mechanical action (endodontic files and irrigation with appropriate solutions). Silver nanoparticles (AgNPs) are well-known for their antibacterial properties, and, for this reason, the aim of this work was to modify the surface of Nickel-Titanium (NiTi) endodontic files with AgNPs, to confer them antimicrobial ability and avoid infections. For this purpose, the preparation and characterization of stable colloids of AgNPs were carried out. Ten NiTi files for endodontics (brand K3 XF, Sybron-Endo Keer) were divided into 2 groups; 5 for group 1 (control, files as received) and 5 for group 2 (files previously coated with AgNPs). Both groups were subjected to biofilm formation using a culture composed of Candida albicans and Enterococcus faecalis, in an anaerobic environment. Endodontic files were successfully modified with silver nanoparticles, and, after exposure under anaerobic conditions to the selected microorganisms. Scanning electron microscopy revealed the proliferation of microorganisms on the surface of the control files. In contrast, the modified and coated files showed no biofilm formation, and the bacteria exhibited changes in cell wall morphology, likely associated with wall rupture and subsequent cell death. The coating of silver nanoparticles on the surface of the files shows to change the morphology of the bacterial wall, causing death and thus inhibition in formation of microbiological biofilms. Since reactive oxygen species (ROS) are unlikely to be present under the anaerobic conditions used, the microbicidal effect of the nanoparticles indicates that ROS-promoted oxidative stress is not an important mechanism of action, and inactivation of thiol-containing proteins could be a more important mechanism.

RESUMEN: El éxito de los tratamientos de endodoncia está relacionado con la neutralización de las bacterias y sus toxinas, dentro y fuera del sistema de conductos radiculares de un diente. Habitualmente esto se consigue, en condiciones ideales, mediante una acción químico-mecánica (limas endodónticas e irrigación con soluciones adecuadas). Las nanopartículas de plata (AgNPs) son conocidas por sus propiedades antibacterianas, por lo que el objetivo de este trabajo fue modificar la superficie de limas endodónticas de Níquel-Titanio (NiTi) con AgNPs, para conferirles capacidad antimicrobiana y evitar infecciones. Se realizó la preparación y caracterización de coloides estables de AgNPs. Diez limas NiTi para endodoncia (marca K3 XF, Sybron-Endo Keer) se dividieron en dos grupos; 5 para el grupo 1 (control, limas tal como se recibieron) y 5 para el grupo 2 (limas previamente recubiertas con AgNP). Ambos grupos fueron sometidos a la formación de biopelículas utilizando un cultivo compuesto por Candida albicans y Enterococcus faecalis, en un ambiente anaeróbico. Las limas endodónticas se modificaron exitosamente con nanopartículas de plata y, después de la exposición en condiciones anaeróbicas a los microorganismos seleccionados. El análisis mediante microscopía electrónica de barrido reveló proliferación de microorganismos en la superficie de las limas de control. En contraste, las limas modificadas y recubiertas no presentaron formación de biopelículas, y las bacterias evidenciaron cambios en la morfología de su pared celular, posiblemente asociados a la ruptura de esta y a la consecuente muerte celular. El recubrimiento de nanopartículas de plata en la superficie de las limas cambia la morfología de la pared bacteriana, provocando la muerte y por lo tanto la inhibición en la formación de biopelículas microbiológicas. Dado que es poco probable que estén presentes especies reactivas de oxígeno (ROS) en las condiciones anaeróbicas utilizadas, el efecto microbicida de las nanopartículas indica que el estrés oxidativo promovido por ROS no es un mecanismo de acción importante, y la inactivación de proteínas que contienen tioles podría ser un mecanismo más importante.

ABSTRACT The rapid conversion of water-soluble carbohydrates in sorghum (Sorghum bicolor (L.) Moench) into lactic acid causes an abrupt decrease in silage pH, promoting alcoholic fermentation and aerobic deterioration. Despite the use of microbial and chemical additives, the results remain inconsistent. Mixing sorghum with cactus pear (Nopalea cochenillifera (L.) Salm-Dyck) can improve the stability and fermentative characteristics of silage. The aim of this study was to determine the ideal level of cactus pear that provides a good microbiological profile, as well as decreases losses during the ensiling process of mixed silages of cactus pear and sorghum. The treatments were composed of levels of cactus pear in the sorghum ensilage (0%, 25%, 50%, 75% and 100% cactus pear on a natural matter basis in the mixture), with four replicates each. It was found a quadratic effect (p < 0.05) on lactic acid bacteria counts, DM recovery and gas losses, with maximum estimated values of lactic acid bacteria and DM recovery in the levels of 51.8% and 33.5% of cactus pear, respectively, and minimum value of gas losses in the level of 37.9% of cactus pear in the silage. An increasing linear effect (p < 0.05) was observed on silage aerobic stability, contents of ether extract and non-fiber carbohydrates. When using cactus pear in the production of mixed silages with sorghum, it is recommended 50% cactus pear in the mixture, as it optimizes DM recovery and aerobic stability of the silages.

ABSTRACT Crop rotation and straw return are important sustainable agricultural practices. However, their combined impact on the soil microbiota is poorly understood. Here, the effects of crop rotation and straw return on rice (Oryza sativa L.) productivity, soil properties and soil microbial community was investigated in a Chinese southern paddy soil. There were six treatments, including rice-fallow (RF), rice-rape (Brassica campestris L.) rotation (RR), rice-edamame (Glycine max (L.) Merr.) rotation (RE), RF with rice straw return (RFS), RR with rice and rape straw return (RRS), and RE with rice and edamame straw return (RES). The results showed that rice yields in RR and RE were increased by 6.28% and 6.93% relative to RF and straw return group increased by 3.03%-8.16% relative to the group without straw return. Rotation increased soil available P (AP) and RRS significantly increased soil organic matter (OM), total N (TN) and available K (AK) in comparison with RR. Rotation impacts soil microbial community in a stronger way than straw return. Rotation increased the bacterial species numbers and fungal Shannon index. Disease-suppressing bacteria were enriched and some fungal pathogen was decreased in rotation treatments. Straw return had no potential risk in increasing the microbial pathogens. Soil fertilities like AK and AP were closely correlated with bacterial alpha-diversity and rice yield. In conclusion, our research demonstrated that combined crop rotation and straw return is an optimum agricultural practice in increasing rice productivity and soil fertility. The impacts of crop rotation and straw return on the microbiota were distinct. These findings help us manage the crops and residues in southern China.

ABSTRACT Water is a vital resource for human survival, being the center of sustainable development. On the other hand, the livestock sector emerges as a major water consumer, producing a substantial volume of nutrient-rich wastewater. Consequently, the feasibility of reusing wastewater and recovering its nutrients becomes necessary to promote the sustainability of water sources. The aim of this study was to generate knowledge about tertiary treatment of wastewater from livestock and poultry industry, the reutilization of water and recovery of its nutrients, and potential applications. A systematic literature review by searching ScienceDirect and Web of Science platforms provides an exploration of technologies that facilitate the reuse of water and recovery of nutrients from livestock and poultry wastewater, including membrane filtration. As a result, the concentrated waste stream from membrane filtration can be utilized by an additional treatment of microalgae, bacteria or synergic consortia of microalgae and bacteria, in particular lactic acid bacteria that are innocuous to humans. Finally, the integration of these technologies presents a promising way to produce valuable biotechnological products with versatile applications in the pharmaceutical and food industries. However, the implementation of these technologies on an industrial scale requires more research.

Abstract Water stress has caused major losses in the agricultural productivity of crops, inducing the search for alternatives for sustainable cultivation. In this context, the objective of this study was to evaluate the tolerance of watermelon under water stress, inoculated with bacterial strains of the genus Bacillus spp., regarding the biochemical and enzymatic variables in the flowering stage. A randomized block design was adopted in a split-plot 4x4 factorial scheme, with plots consisting of four levels of soil water availability (40%, 60%, 80% and 100% of field capacity - FC) and subplots consisting of four inoculations (Negative Control (NC); XX6.9 bacteria; P6.2 bacteria; MIX - co-inoculation of XX6.9 and P6.2 bacteria), with five replicates. XX6.9 bacteria and NC were the treatments most affected by severe water stress, since at the soil water availability (SWA) level of 40% FC they showed high contents of the oxidative marker (MDA) and proline. Although the inoculation with XX6.9 bacteria promoted a higher content of osmoregulators such as proteins, total soluble sugars and reducing sugars, it was not enough to attenuate the effects of water deficit. On the other hand, treatments with P6.2 bacteria and MIX of bacteria showed reduced levels of MDA at the SWA level of 40% FC, accompanied by high enzymatic activity of POD and CAT, which may contribute to the tolerance of the watermelon crop to water stress.

ABSTRACT One of the main phytosanitary problems in major crops are phytonematodes, which are characterised as difficult to control. In view of this, biocontrol, through the use of biological agents, has become a driving force in controlling these pathogens. The aim of this study was to evaluate the compatibility of microorganisms, and detect the possibility of antagonistic effects, influence on growth, or synergistic action when microorganisms are jointly applied to crops. Microbiological analyses were carried out to observe the interaction of the fungus Trichoderma asperellum with the bacteria Bacillus subtilis and Bacillus methylotrophicus. It was found that the interaction between the genera Bacillus and Trichoderma did not promote any increase in the fresh or dry weight of the roots or shoots of the soya plants; however, based on the results of the microbiological analysis of the fungi and bacteria, the interaction was found to be promising, particularly in the evaluation carried out on the seventh day. Considering the number of viable spores, the interaction between B. subtilis + T. asperellum showed better results than B. methylotrophicus + T. asperellum. The Interaction between the genera Bacillus and Trichoderma showed the potential for joint use in the biological control of the soya bean.

ABSTRACT Rhodococcus equi is an opportunistic soil-borne bacterium that is eliminated in feces of multi-host animals. An increase in multidrug-resistant R. equi isolates has been reported in humans and domestic animals, and it has been hypothesized that the treatment of R. equi in foals could increase the selective pressure on multidrug-resistant isolates and favor human infections by resistant isolates. We investigated the in vitro antimicrobial susceptibility/resistance of 41 R. equi strains from humans, which were isolated from patients with pulmonary signs, using 19 antimicrobials from 10 distinct classes, recommended exclusively to humans, recommended exclusively to domestic animals and used in both. All isolates were subjected to mass spectrometry and identified as R. equi. Among the antimicrobials used exclusively in humans, tigecycline and vancomycin showed 100% efficacy. Amikacin, amoxicillin/clavulanic acid, imipenem, levofloxacin, clarithromycin, rifampin, ciprofloxacin, and gentamicin, used in both humans and animals, revealed high efficacy (97–100%). Conversely, a higher frequency of isolates was resistant to penicillin (87.8%) and trimethoprim/sulfamethoxazole (43.9%), which are used in both humans and animals. Among the antimicrobials used only in animals, isolates were resistant to florfenicol (46.4%), ceftiofur (17.1%), and enrofloxacin (2.5%). Multidrug resistance was observed in 34% of isolates. The identification of drug-resistant R. equi isolated from humans used exclusively in animals is circumstantial evidence of the pathogen transmission from domestic animals to humans. This study contributes to the molecular identification of Rhodococcus species from humans and to the epidemiological vigilance of the multidrug-resistant isolates.

ABSTRACT Breeding of new cultivars of sugarcane uses several species belonging to the Saccharum complex genus. In this study, a set of 20 genotypes from the Saccharum complex was assessed for their growth promotion during germination using a mixed inoculant containing five selected diazotrophs and their resistance to short heat treatment (52°C / 30 min). The percentage of germination was evaluated, leading to the identification of three response groups. Saccharum officinarum (group I) showed the highest germination percentage, succeeded by Erianthus arundinaceus genotypes (group II) and the other genotypes (group III). The mean germination time (MGT) varied among the genotypes and segregated the growth response into two groups. Saccharum officinarum only required less than 15 days to reach the MGT, whereas the other genera required more than two or three days during the initial growth process. Bacterial counting also differed between the groups, being effective for S. officinarum and other genotypes, improving the colonization of the plants 100–1,000 times higher than the control and heat treatments. Further comparison was made among eight genotypes, including one Saccharum spontaneum(US72-1319), one S. officinarum (IN845), and six E. arundinaceus. This comparison measured biomass accumulation and root parameters. The E. arundinaceus group demonstrated less susceptibility to the heat treatment, resulting in stimulation of the root dry mass of IJ76-381 and root parameters of this genotype, as well as IJ76-364, although not associated to the inoculation treatment. Inoculation applied to US72-1319 and IN845 enhanced only the Shoot/Root ratio.

ABSTRACT Introduction: The Brazilian Society of Nephrology estimates that approximately 10 million people in Brazil had chronic kidney disease in 2019. In 2022, 5,303 kidney transplants were performed in the country, with the city of Juiz de Fora standing out as one of the largest reference centers for kidney transplants. Objectives: The objective of this study is to evaluate the occurrence of urinary tract infections in post-transplant patients, as well as the type of infection. Methods: This is a retrospective quantitative cross-sectional study in which data from the medical records of patients who underwent kidney transplantation from 2019 to 2022 were analyzed. Results: Of a total of 537 kidney transplants performed during this period, 64 urinary tract infections associated with urinary catheters were observed in the first 30 days post-transplantation, with a higher incidence in the first 5 days. Most of the microorganisms observed belong to the human microbiota, indicating that the cause may be related to catheterization, the hospital environment, or the patient. The infections observed are caused by bacteria resistant to the antibiotics trimethoprim and sulfamethoxazole, such as Escherichia coli, Klebsiella sp., and Serratia sp. Conclusion: The study indicates that it is necessary to improve the handling of the patients and materials to reduce infections, mainly due to the high degree of antibiotic resistance of the microorganisms observed.

RESUMO Introdução: A Sociedade Brasileira de Nefrologia estimou que cerca de 10 milhões de pessoas no Brasil tinham doença renal crônica em 2019. Em 2022, 5.303 transplantes renais foram realizados no país, destacando-se o município de Juiz de Fora como um dos maiores centros de referência em transplantes renais. Objetivos: O objetivo deste trabalho é avaliar a ocorrência de infecções no trato urinário de pacientes pós-transplante, bem como o tipo de infecção. Métodos: Trata-se de estudo transversal, quantitativo e retrospectivo, no qual dados dos prontuários dos pacientes que realizaram transplante renal de 2019 a 2022 foram analisados. Resultados: Do total de 537 transplantes renais realizados nesse período, foram observadas 64 infecções do trato urinário associadas ao cateter vesical nos primeiros 30 dias pós-transplante, com maior incidência nos primeiros 5 dias. A maior parte dos microrganismos observados pertence à microbiota humana, indicando que a causa pode estar relacionada ao cateterismo, ao ambiente hospitalar ou ao próprio paciente. As infecções são causadas por bactérias resistentes aos antibióticos trimetoprima e sulfametoxazol, como Escherichia coli, Klebsiella sp. e Serratia sp. Conclusão: O trabalho aponta que é necessário melhorar a manipulação dos pacientes e materiais, visando reduzir as infecções, principalmente em função do alto grau de resistência a antibióticos dos microrganismos observados.

Abstract Antimicrobial drug resistance is a challenge to public health. Various microorganisms, including methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, carbapenemase-producing Klebsiella pneumoniae, Pythium insidiosum, and Candida auris, have developed resistance to commonly used antimicrobials in infection disease treatments. Consequently, there is an urgent need to explore and develop novel therapeutic drugs. Natural products, particularly medicinal plants, have received attention in the quest for innovative treatments for various diseases. Plantago major is a plant endowed with several biological properties, such as antibacterial, antifungal, and healing actions. This study aimed to investigate the antimicrobial activities of the methanolic extract obtained from the leaves of P. major. Microdilution assays were conducted to determine the minimum inhibitory concentration and minimum bactericidal and fungicidal concentration. Additionally, synergism with antimicrobial drugs was assessed using a time-kill curve analysis. A synergistic bactericidal interaction between the extract and imipenem was observed against carbapenemase-producing K. pneumoniae. For MRSA, a bacteriostatic synergism was noted in combinations of the extract with cephalotin and oxacillin. For C. auris, a fungistatic interaction was observed between the extract and amphotericin B. These results suggest the presence of bioactive compounds within the extract with therapeutic potential for combating infections caused by these microorganisms.

Abstract Hybrid structures containing multiple pharmacophore units with known activity have attracted attention due to their promising outcomes. In this study, several new hybrid structures containing benzimidazole and thiadiazole units were synthesized. The newly synthesized compounds were structurally analyzed using 1H-NMR, 13C-NMR, HRMS, and elemental analysis. The antimicrobial, in vitro anti-cancer, and antioxidant activities of all compounds were investigated. In vitro antimicrobial activities of the compounds were determined against Gram-positive (S. aureus ATCC 29213, E. faecalis ATCC 29212), Gram-negative (E. coli ATCC 25922, P. aeruginosa ATCC 27853) bacteria and fungi (C. albicans ATCC 10231) by using broth microdilution method. The compound 5g bearing 4-methoxyphenyl derivative showed the best activity with 32 μg/mL against S. aureus ATCC 29213 and P. aeruginosa ATCC 27853. The MTT test was used to determine the cytotoxicity of the produced compounds on the MCF-7 (human breast cancer) and L-929 (fibroblast) cell lines. FRAP method was used to determine the antioxidant properties of synthesized compounds. The Ferric Reducing Antioxidant Power of the compounds 5a, 5b, and 5c showed more antioxidant properties than vitamin E. The compound 5g stands out in the series in that it is not toxic on the healthy cell line and has promising antimicrobial activity.

Abstract Background Treating NDM-producing bacteria poses a significant challenge, especially for those bacteria inherently resistant to polymyxin, such as Serratia marcescens, necessitating combined therapies. Objective To assess in vitro the synergistic effect of different antimicrobial combinations against NDM-producing S. marcescens. Methods Four clinical isolates were tested with various antibiotic combinations: polymyxin, amikacin, meropenem, and aztreonam. Concentrations used were those maximized by pharmacokinetic and pharmacodynamic assessments. Synergy evaluation involved a static macrodilution test followed by a time-kill curve assay. Results All four isolates demonstrated resistance according to CLSI and EUCAST standards for the tested antibiotics (polymyxin, amikacin, meropenem, and aztreonam). In the macrodilution synergy test, the combination of aztreonam and amikacin was active in 2 out of 4 isolates within 24 h, and polymyxin with meropenem in only one isolate, despite of intrinsic resistance to polymyxin. However, time-kill curve analysis revealed no synergism or additive effect for combinations with the tested antimicrobials. Conclusion Combinations of polymyxin, meropenem, aztreonam, and amikacin at doses optimized by pharmacokinetic/pharmacodynamic were insufficient to demonstrate any synergism in NDM-producing S. marcescens isolates in time-kill curves.